Fears are being raised that widening the Albany Highway will come at the expense of native wildlife.
Part of Auckland Transport's $70 million widening project involves expanding Days Bridge to four lanes.
But students at nearby Albany Senior College fear work above Oteha Valley Stream will spoil the waterway.
Former student and aquarium company owner Ross McWilliams, 19, who assists students with projects involving the stream, says a water diversion has already "ruined" the stream.
In July 2012, sandbags used by contractors to temporarily manage the water flow split open, depositing four tonnes of sand into the stream, McWilliams says.
Year 13 student William Pearman, 17, who has since been monitoring the waterway with school mates, says it's still recovering from the incident.
"When I walk through the creek now, the substrate is still pretty much all sand," the budding ecologist says.
The sand has "pretty much" wiped out downstream species, including natives such as the torrent fish which requires fast-moving water, Pearman says.
Native eel numbers and vegetation have taken a hit as well, he says.
Construction waste from pipe-laying along the highway, just metres from the creek also washed into the stream, McWilliams says.
"I'm really concerned they might sandbag the stream again which could permanently destroy it," he says.
Auckland Transport (AT) media manager Mark Hannan acknowledges some disturbance to the waterway during the new construction is unavoidable.
But before work starts in September, contractors will have to submit an environmental management plan, he says.
AT is confident any disturbances to the stream's flora and fauna can be re-established once work is complete, Hannan says.
AT is "more than happy to sit down" with the school and students to brief them on what's planned and safeguards being putting in place, he says.
- North Shore Times
Is the cost of electricity forcing you to rethink your power consumption this winter?